Light source and organic laser click-in

Abstract

The present invention provides a highly efficient organic laser element 1 in which optical absorption loss and optical leakage in the waveguide are reduced. [Solution] The device comprises a light incident surface (first surface Sf1) into which light is incident, a light exit surface (second surface Sf2) intersecting the light incident surface, and a groove-shaped waveguide (trench waveguide 8) formed across the light incident surface and the light exit surface. The waveguide is provided with a DFB grid 4 having repeatedly formed protrusions 5 and grooves 6, each of which extends in a direction intersecting the light incident surface, and furthermore, the protrusions 5 and grooves 6 intersect in the direction in which the waveguide extends toward the light exit surface.

Description

Technical Field

[0001] The present invention relates to a light source and an organic laser device, and particularly to a light source with amplified spontaneous emission, an optically pumped organic solid-state laser device having a distributed feedback structure, and a current injection type organic semiconductor laser device.

Background Art

[0002] An organic laser device having an active layer composed of an organic material has rich selectivity in oscillation wavelength because almost an infinite number of light-emitting materials can be selected by molecular design of the organic material, and can be manufactured at low cost by using a coating / printing process. Further, various advantages such as imparting flexibility to the laser device and contributing to weight reduction can be considered. As a technology related to such an organic laser device, for example, a current injection type organic semiconductor laser (OSLD: Organic Semiconductor Laser Diode) in which a distributed feedback (DFB (Distributed feedback)) structure is arranged between a pair of electrodes, an organic laser active layer, and a pair of electrodes is known. (Patent Document 1)

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Disclosure of the Invention

Problems to be Solved by the Invention

[0004] The technology described in Patent Document 1 realizes OSLD by introducing a DFB structure into the architecture of an organic light-emitting diode (OLED). Conventional organic laser elements have an organic waveguide between two electrodes that includes a light-emitting layer made of an organic gain material. Each convex and groove in the DFB structure is extended along the plane formed by the two electrodes, and the convex and groove are repeatedly formed in directions perpendicular to their respective extension directions (hereinafter, this structure may be referred to as a "horizontal DFB structure"). Laser light is then emitted from the end faces in the directions in which the convex and groove are repeatedly formed.

[0005] In organic laser elements employing a horizontal DFB structure, the refractive indices of adjacent layers to the organic waveguide differ significantly. This results in an asymmetrical cross-section of the electromagnetic energy density distribution in the organic waveguide, causing large penetration of evanescent waves into one of the adjacent layers and leading to increased optical absorption loss.

[0006] Furthermore, in organic laser elements with a horizontal DFB structure, the vibration direction of the TE mode wave (TE mode polarization) is parallel to the planes of the two electrodes and also parallel to the plane formed by the horizontal DFB structure. Since ITO, which constitutes one of the electrodes, has a higher refractive index than most organic materials, some of the light propagating within the organic waveguide leaks through the ITO slab, resulting in insufficient light confinement within the waveguide. In addition, although metals such as silver and aluminum that constitute the other electrode have high reflectivity, evanescent waves penetrate the metal layer to some extent, causing absorption by metal atoms and ultimately hindering light amplification.

[0007] The present invention was devised to solve the problems of the prior art, and its objective is to provide a highly efficient light source and an organic laser element that reduce light absorption loss and light leakage in the waveguide. [Means for solving the problem]

[0008] The present invention provides a light source comprising a groove-shaped waveguide formed to a predetermined length (trench length TL), a predetermined width (effective trench width ETW), and a predetermined height (trench height TH), wherein the waveguide satisfies the relationship effective trench width ETW < trench height TH < trench length TL, and when the direction in which the waveguide extends over the trench length TL is defined as the longitudinal direction, the waveguide has smooth side walls that are parallel and opposite to each other along the longitudinal direction, and emits naturally radiated amplified light from the end face of the waveguide in the longitudinal direction. This reduces light absorption loss and light leakage, and provides a light source that emits high-intensity light.

[0009] Furthermore, the present invention provides an organic laser element comprising a light incident surface for receiving light, a light output surface intersecting the light incident surface, and a groove-shaped waveguide formed across the light incident surface and the light output surface, wherein the waveguide is provided with a DFB grating in which convex portions and groove portions are repeatedly formed, and each of the convex portions and groove portions extends in a direction intersecting the light incident surface, and furthermore, the extension directions of the convex portions and groove portions intersect with the direction in which the waveguide extends toward the light output surface. This provides a highly efficient organic laser element (photo-excited organic solid-state laser element) with reduced light absorption loss and light leakage.

[0010] Furthermore, the present invention provides an organic laser element comprising two electrodes and a groove-shaped waveguide provided between the two electrodes, wherein the waveguide is provided with a DFB lattice having repeatedly formed convex portions and groove portions, and each of the convex portions and groove portions is extended in a direction intersecting the electrodes. This reduces light absorption loss and light leakage, resulting in a highly efficient organic laser element (current-injection type organic semiconductor laser element) with a low threshold and long operating life. In addition, increasing the thickness of the OLED structure contained in the organic laser element (the distance between the pair of electrodes) improves the stability of the element and extends the operating life. Moreover, even under high voltage, it is prevented that charge carriers reach the counter electrode, improving charge recombination efficiency and thus improving the external quantum efficiency (EQE). [Effects of the Invention]

[0011] Thus, according to the present invention, a highly efficient light source and a highly efficient organic laser element can be obtained, which reduce optical absorption loss and optical leakage in the waveguide. [Brief explanation of the drawing]

[0012] [Figure 1] (A) is a top view of the trench waveguide 8 in the light source 25 according to the first embodiment of the present invention, and (B) is a perspective view thereof. [Figure 2] (A) is an explanatory diagram showing the simulation results of the electromagnetic energy density distribution of a conventional slab waveguide 35, and (B) is an explanatory diagram showing the simulation results of the electromagnetic energy density distribution of a trench waveguide 8. [Figure 3] (A) and (B) are explanatory diagrams showing the simulation results for a waveguide array 15 equipped with multiple trench waveguides 8. [Figure 4] A perspective view showing an overview of the trench waveguide 8 in the organic laser element 1 according to the second embodiment of the present invention. [Figure 5] (A) to (C) are explanatory diagrams showing examples of the configuration of a trench waveguide 8 equipped with a vertical DFB structure. [Figure 6] Diagram illustrating a waveguide array 15 composed of multiple trench waveguides 8 with a vertical DFB structure. [Figure 7] Diagram illustrating the long-range laser beam interference pattern. [Figure 8] Diagram illustrating the manufacturing process of OSL device 16. [Figure 9] Perspective view showing the configuration of the encapsulated OSL device 16. [Figure 10] Diagram illustrating the configuration of an inert gas-filled chamber (chamber 39) designed for end-face emission measurement. [Figure 11] This diagram illustrates the configuration of the end-face emission measuring device 40 for measuring end-face emission from the OSL device 16. [Figure 12] Diagram illustrating the overview of a conventional OSLD device with a horizontal DFB structure. [Figure 13]Cross-sectional view of a conventional horizontal DFB structure including an OSLD [Figure 14] (A) to (D) are explanatory diagrams showing the configuration of the organic laser element 1 (OSLD device 17 including a vertical DFB structure) according to the third embodiment of the present invention [Figure 15] Microscopic image of a trench waveguide 8 array having a vertical DFB structure formed on ITO [Figure 16] Cross-sectional view of an OSLD device 17 including a vertical DFB structure [Figure 17] Explanatory diagram for explaining the manufacturing process of the OSLD device 17 [Figure 18] (A) is an explanatory diagram of the OLED structure used for evaluation, and (B) and (C) are characteristic diagrams of the OLED in which the thickness of the light-emitting layer (EML) is changed from 200 nm to 1400 nm [Figure 19] Explanatory diagram showing the configuration of an end-face light emission measuring device 40 for measuring end-face light emission from the OSLD device 17 [Figure 20] Explanatory diagram showing examples of organic gain materials used in the light source 25 of the first embodiment and the organic laser element 1 of the second and third embodiments [Figure 21] (A) is an explanatory diagram showing a configuration example of a multilayer OLED introduced into the OSLD device 17, and (B) is an explanatory diagram showing a configuration example of a single-layer OLED introduced into the OSLD device 17

Mode for Carrying Out the Invention

[0013] (First Embodiment) Figure 1(A) is a top view of the trench waveguide 8 in the light source 25 according to the first embodiment of the present invention, and (B) is a perspective view thereof. The trench waveguide 8 has a form in which a portion of the first surface Sf1 and a second surface Sf2 perpendicular to the first surface Sf1 of a frame 13 of a predetermined shape (here, a rectangular parallelepiped) are cut out in a groove shape. Here, the second surface Sf2 constitutes the end surface from which light is emitted. Specifically, the trench waveguide 8 is composed of a groove (cavity, trench) having a predetermined length (hereinafter sometimes referred to as "trench length TL"), a predetermined width ETW (hereinafter sometimes referred to as "effective trench width ETW"), and a predetermined height (depth) (hereinafter sometimes referred to as "trench height TH") along the longitudinal direction (x direction) of the frame 13.

[0014] Here, trench waveguide 8 is Effective trench width ETW < Trench height TH < Trench length TL It has a shape that satisfies the following conditions. The effective trench width ETW refers to the distance between the two opposing side walls 7 in the trench waveguide 8.

[0015] For example, in terms of specific dimensions, Effective trench width ETW = 150nm~250nm Trench length TL = 1mm to 3mm Trench height TH = 500nm ~ 2000nm It can be done this way.

[0016] The frame 13 is made of, for example, SiO2, which is a hard inorganic glass. The frame 13 may also be made of a resin material, for example, polymethyl methacrylate (PMMA), amorphous fluoropolymer (e.g., CYTOP®), or cycloolefin polymer (COP) can be used.

[0017] As shown in Figure 1(A), the trench waveguide 8 has smooth sidewalls 7 that are parallel and opposite to each other along the longitudinal direction (the direction in which the trench waveguide 8 extends over the trench length TL). The trench waveguide 8 is filled with an organic gain material (luminescent material). In this configuration, when light is generated by the organic gain material, no perturbation occurs in the propagating light within the trench waveguide 8, and no feedback occurs. Therefore, when a configuration is introduced in which excitation light is incident from the first surface Sf1 to the organic gain layer 9 (referencing Figure 9) or when current is injected into the organic gain material (referencing Figure 14) in the trench waveguide 8 of the first embodiment, which is filled with organic gain material, amplified spontaneous emission (ASE) based on optical pumping or current injection is emitted from the longitudinal end face (second surface Sf2) of the trench waveguide 8 (frame 13).

[0018] Figure 2(A) is an explanatory diagram showing the simulation results of the electromagnetic energy density distribution of a conventional slab waveguide 35, and Figure 2(B) is an explanatory diagram showing the simulation results of the electromagnetic energy density distribution of a trench waveguide 8. Both Figures 2(A) and (B) show cross-sectional views of the electromagnetic energy density distribution within the waveguide. Here, Figure 2(B) is the simulation result for the trench waveguide 8, in which both side walls 7 have equal refractive indices and function as a cladding layer, as described above. The simulation used the OMS online 1-D mode solver for the analysis of multiple dielectric thin film waveguides (https: / / www.computational-photonics.eu / oms.html).

[0019] The parameters used in the simulation are as follows: (1) Slab waveguide 35 shown in Figure 2(A) • Thickness of slab waveguide 35 = 200 nm • Refractive index of the organic gain layer 9 constituting the waveguide = 1.8 • Wavelength of light propagating through a waveguide = 480nm (sky blue) • Refractive index of the substrate 12 (assuming SiO2) of the slab waveguide 35 = 1.45 • Refractive index of air = 1.0 (2) Trench waveguide 8 shown in Figure 2(B) Effective trench width ETW = 200 nm • Refractive index of the organic gain layer 9 filled in the trench waveguide 8 = 1.8 • Wavelength of light propagating through trench waveguide 8 = 480nm (sky blue) • The refractive index of the frame 13 (assuming SiO2) constituting the trench waveguide 8 = 1.45 In the simulation for trench waveguide 8, the electromagnetic energy density distribution in the trench width direction is the target of evaluation, so the trench length TL and trench height TH are not included as parameters.

[0020] As shown in Figure 2(A), the electromagnetic energy density distribution in a conventional slab waveguide 35 (i.e., a waveguide in contact with air (refractive index = 1.00) and SiO2 (refractive index = 1.45)) shows an asymmetrical cross-section. However, as shown in Figure 2(B), the trench waveguide 8 according to the present invention shows a symmetrical cross-section in terms of electromagnetic energy density distribution. From this, it can be seen that the trench waveguide 8 has a higher light confinement effect compared to the slab waveguide 35.

[0021] As shown in Figure 2(B), light within the trench waveguide 8 is totally reflected and confined by the relatively high refractive index (here, 1.8) of the organic gain material contained in the organic gain layer 9 and the relatively low refractive index (here, 1.45) at the interface of the sidewall portion 7 (see Figure 1) made of SiO2. Although the evanescent wave of the propagating light is transmitted to some extent through the sidewall portion 7 made of SiO2, there is no absorption of electromagnetic waves in the UV (Ultraviolet), visible, and IR (Infrared) regions. Furthermore, since the refractive indices of the opposing sidewall portions 7 are all the same (here, 1.45), the electromagnetic energy density distribution forms a symmetrical cross-section, and maximum energy propagation is achieved at the center in the width direction of the trench waveguide 8.

[0022] Figures 3(A) and 3(B) are explanatory diagrams showing simulation results for a waveguide array 15 equipped with multiple trench waveguides 8. Hereafter, in a waveguide array provided with multiple trench waveguides 8, the thickness of the frame 13 separating two adjacent trench waveguides 8 may be referred to as the "trench spacing TS" (see Figures 6 and 16). Here, Figure 3(A) corresponds to a waveguide array in which three trench waveguides 8 are provided with a trench spacing TS + effective trench width ETW (i.e., the arrangement period of the trench waveguides 8 in the waveguide array 15 (hereinafter sometimes referred to as the "trench period PTA"; see Figures 6 and 7)) = 1.2 μm, and Figure 3(B) corresponds to a waveguide array similarly provided with five trench waveguides 8. Here, the trench spacing TS = 1.0 μm and the effective trench width ETW = 0.2 μm. The solver and parameters used in the simulation are the same as those described using Figure 2(B). As shown in the figure, the array equipped with trench waveguides 8 significantly amplifies the light.

[0023] Thus, the light source 25 of the first embodiment includes a groove-shaped waveguide (trench waveguide 8) formed to a predetermined length (trench length TL), a predetermined width (effective trench width ETW), and a predetermined height (trench height TH). The waveguide satisfies the relationship effective trench width ETW < trench height TH < trench length TL, and when the direction in which the waveguide extends over the trench length TL is defined as the longitudinal direction, the waveguide has smooth sidewalls 7 that are parallel and opposite to each other along the longitudinal direction, and emits naturally radiated amplified light from the end face in the longitudinal direction of the waveguide. In other words, the light source 25 of the first embodiment functions as a naturally radiated amplified light source. The light source 25 of the first embodiment reduces light absorption loss and light leakage in the trench waveguide 8 and further amplifies the light significantly. Therefore, when the trench waveguide 8 is introduced into the organic laser element 1 (see Figures 9 and 14), it becomes possible to lower the oscillation threshold of the organic laser element 1 (the minimum amount of excitation light, current, or voltage required to obtain laser light; the same applies hereinafter).

[0024] Furthermore, in the first embodiment, the light source 25 has the same refractive index for the opposing side walls 7, and the trench waveguide 8 is filled with a gain material having a higher refractive index than the side walls 7. This reduces light absorption loss and light leakage in the trench waveguide 8. In addition to organic materials, inorganic materials and organic-inorganic hybrid materials, which will be described later, may also be used as the gain material.

[0025] (Second Embodiment) Figure 4 is a perspective view showing an overview of the trench waveguide 8 in the organic laser element 1 according to the second embodiment of the present invention. As shown in the figure, the trench waveguide 8 has a DFB grid 4 in which protrusions 5 and grooves 6 are repeatedly formed on the side wall portion 7 of the frame 13. Both the protrusions 5 and grooves 6 constituting the DFB grid 4 extend in the height direction (z direction) of the trench waveguide 8 and are repeatedly formed in the longitudinal direction (x direction (direction from which light is emitted)) of the trench waveguide 8 (hereinafter, this configuration may be referred to as the "vertical DFB structure"). By introducing the vertical DFB structure to the trench waveguide 8, the vibration direction of the TE mode wave becomes parallel to the extension direction (z direction) of the protrusions 5 and grooves 6. In the trench waveguide 8 equipped with the vertical DFB structure, the frame 13 is made of, for example, SiO2. Of course, the resin material described above may also be used.

[0026] As will be described later, in the second embodiment, trench waveguides 8 are formed in the SiO2 layer constituting the frame 13 using reactive ion plasma etching or the like. Because of this manufacturing process, the DFB grid 4 (i.e., protrusions 5, grooves 6) in the trench waveguide 8 can be formed in any shape, spacing, and pitch (period). Specifically, the effective trench width ETW may be, for example, 150 nm to 250 nm, the trench length TL may be, for example, 1 mm to 3 mm, and the trench height TH may be, for example, 500 nm to 2000 nm. As is clear from the manufacturing process, in the second embodiment as well, the refractive indices of the opposing sidewalls 7 are the same. Furthermore, the trench waveguide 8 with a vertical DFB structure is filled with an organic gain material having a refractive index higher than the refractive index of the sidewalls 7 (e.g., 1.8) (e.g., 1.45). The organic gain material constitutes the organic gain layer 9.

[0027] Figures 5(A) to 5(C) are explanatory diagrams showing example configurations of trench waveguides 8 equipped with a vertical DFB structure. Any of these configurations can be applied to an organic laser element 1. As shown in Figures 5(A) to 5(C), when a DFB grid 4 (vertical DFB structure) is formed on the sidewall portion 7 of the trench waveguide 8 to introduce a small perturbation into the propagation of the waveguide, feedback occurs within the trench waveguide 8. Stimulated emission (optical amplification by stimulated emission of laser radiation) is then observed from the longitudinal end face of the trench waveguide 8. That is, the trench waveguide 8 equipped with a vertical DFB structure functions as an optical resonator. The laser wavelength and laser oscillation threshold can be adjusted by the dimensions of the vertical DFB structure, the dimensions of the trench waveguide 8, and the number of periodically arranged grooves 6.

[0028] Here, Figure 5(A) shows an example in which a DFB grid 4 is provided on one side wall 7. Figures 5(B) and (C) show examples in which a DFB grid 4 is provided on both side wall 7s. In these examples, the vertical DFB structure is composed of DFB grids 4 with two different phases. In the example shown in Figure 5(B), the phase in which the convex portions 5 and groove portions 6 of the DFB grid 4 provided on one side wall 7 are repeated is called the first phase, and the phase in which the convex portions 5 and groove portions 6 of the DFB grid 4 provided on the other side wall 7 are repeated is called the second phase, in which the first phase and the second phase are the same (i.e., the shape of each DFB grid 4 is symmetrical with respect to the zx plane containing axis Ax).

[0029] On the other hand, in the example shown in Figure 5(C), when the phase in which the convex portions 5 and groove portions 6 of the DFB grid 4 provided on one side wall portion 7 are repeated is defined as the first phase, and the phase in which the convex portions 5 and groove portions 6 of the DFB grid 4 provided on the other side wall portion 7 are repeated is defined as the second phase, the first phase and the second phase are inverted from each other (shifted by the first DFB period P / 2 (half period)). Of course, the first phase and the second phase can be changed as appropriate, for example, an intermediate configuration between Figure 5(B) and Figure 5(C) may be used. That is, the first phase and the second phase can be shifted as appropriate between being the same and being inverted.

[0030] In any of the configurations shown in Figures 4 and 5(A) to (C), the refractive index of the frame 13 is the same at both side walls 7 of the trench waveguide 8, making it possible to reduce light absorption loss and light leakage. Therefore, these trench waveguides 8 can be suitably applied to the organic laser element 1.

[0031] In the second embodiment as well, the trench waveguide 8 has a shape that satisfies the conditions effective trench width ETW < trench height TH < trench length TL. The effective trench width ETW represents the distance between two opposing side wall portions 7 in the trench waveguide 8. However, if a DFB grid 4 is provided on the side wall portion 7 as shown in Figure 5, the position of the side wall portion 7 in the y-direction is determined based on the ratio of the area occupied by the convex portion 5 to the area occupied by the groove portion 6. For example, if the area occupied by the convex portion 5 is 50%, the effective trench width ETW is determined by assuming that the side wall portion 7 is located at a position of convex portion height PH / 2 (see also Figure 4).

[0032] Figure 6 is an explanatory diagram showing a waveguide array 15 composed of multiple trench waveguides 8 having a vertical DFB structure. The waveguide array 15 can be applied to organic laser elements 1, such as the OSL device 16 (OSL: Organic Solid-state Laser) according to the second embodiment, or the OSLD device 17 according to the third embodiment, which will be described later. In Figure 6, the waveguide array 15 includes five trench waveguides 8 arranged with a trench period PTA. Of course, the number N of trench waveguides 8 can be arbitrarily selected. Here, the effective trench width ETW, trench length TL, and trench height TH of each trench waveguide 8 can be the values ​​explained using, for example, Figure 4. Also, the trench period PTA can be, for example, 1.2 μm. When the waveguide array 15 is introduced into the organic laser element 1, the trench height TH, trench spacing TS, effective trench width ETW, trench length TL, and the number of trench waveguides N all have an overall effect on the laser threshold, gain coefficient, and laser output.

[0033] Figure 7 is an explanatory diagram illustrating the far-field laser beam interference pattern. In the organic laser element 1 using the waveguide array 15 described above, the trench period PTA shown in Figure 6 affects the far-field interference beam angles. In the waveguide array 15, when the trench period PTA is smaller than the desired laser oscillation wavelength, the far-field laser beam interference pattern is observed as a single bright fringe. On the other hand, when the trench period PTA is larger than the desired laser oscillation wavelength, the exit slit at the end face (the opening of the trench waveguide 8 at the end face) functions like a multiple slit under Fraunhofer diffraction conditions. Therefore, the far-field laser beam interference pattern is d sinθ = nλ···(Equation 1) This resembles the multi-slit diffraction pattern under Fraunhofer conditions. That is, a far-field laser beam interference pattern consisting of several dark and bright fringes is observed, similar to the interference pattern from multiple slits or diffraction gratings. Note that the trench period PTA corresponds to "d" in (Equation 1). If the phases of the waves emitted from all the slits (trench waveguide 8) are aligned, the maximum intensity is observed in the fringe pattern shown in Figure 7. This further confirms the coherence and monochromaticity of the laser.

[0034] Figure 8 is an explanatory diagram showing the manufacturing process of the OSL device 16. Below, the manufacturing process of the OSL device 16 as an organic laser element 1 will be explained using Figure 8 in combination with Figures 4 and 6. First, fused silica glass (substrate 12) is prepared. Next, an SiO2 layer, which is the material that constitutes the frame 13 (see Figure 4, etc.), is formed on the substrate 12 by sputtering. Here, the SiO2 layer is formed to be very thick (for example, 500 nm to 2000 nm). Next, a resist layer is formed on the SiO2 layer using the spin coating method. Next, a nanopattern mask is created by electron beam lithography, and a trench waveguide 8 (see Figure 4, etc.) with a vertical DFB structure is created by reactive ion plasma etching and solvent cleaning. As a result, the trench waveguide 8 (waveguide array 15) is formed on the frame 13, and a DFB grid 4 (primary vertical DFB) is formed on its side wall portion 7. The trench waveguide 8 with a vertical DFB structure functions as an optical resonator.

[0035] Furthermore, the materials constituting the frame 13 preferably satisfy the following conditions. (I) It must have high transmittance to the target laser oscillation wavelength (i.e., the evanescent wave must not be absorbed). (II) Low refractive index (to form a total reflection waveguide and generate feedback). (III) The trench waveguide 8 can be nanopatterned (it is possible to engrave the nanopattern by a top-down approach using electron beam lithography, photolithography, reactive ion plasma etching, wet etching, focused ion beam lithography, etc., or by a bottom-up approach using electron beam-induced deposition (EBID), etc.). SiO2, a hard inorganic glass, satisfies conditions (I) to (III).

[0036] Furthermore, as a condition (IV) It must be electrically insulated (charge carriers must not pass through it). The following may be added. In particular, it is preferable that the frame 13 of the OSLD device 17, which will be described later, satisfies all of (I) to (IV), and for example, SiO2 satisfies all of these conditions. The frame 13 can also be made of the resin material described in the first embodiment.

[0037] Next, an organic laser amplification material (organic gain material) is filled into the trench waveguide 8 to form an organic gain layer 9 (see Figure 4). At this time, the organic gain material is deposited in the trench waveguide 8 until it reaches the same level as or exceeds the upper surface of the frame 13. That is, the trench waveguide 8 is an organic waveguide including the organic gain layer 9, and the thickness of the organic gain layer 9 is substantially the same as the depth of the trench waveguide 8 (trench height TH). In addition to organic materials (single molecules, macromolecules, polymers, quantum dots, etc.), inorganic materials (laser-activated crystals, quantum dots, etc.) and organic-inorganic hybrid materials (perovskite, etc.) can be used as the gain material deposited (filled) in the trench waveguide 8.

[0038] Next, the frame 13 and substrate 12, on which the trench waveguide 8 containing the organic gain layer 9 is formed, are cut along the A-B line shown in Figure 8 in a glove box filled with inert gas. The number of trench waveguides 8 formed in the above process is arbitrary and can be, for example, one, two, or more, as shown in the figure. In this way, an end-face emitting type organic laser element 1 (OSL device 16) that emits laser light from the cut end face is obtained. The obtained organic laser element 1 is fixed in a chamber filled with inert gas in order to measure its characteristics. Alternatively, it can be sealed and encapsulated.

[0039] Figure 9 is a perspective view showing the configuration of the encapsulated OSL device 16. The OSL device 16, i.e., the organic laser element 1 according to the present invention, consists of a frame 13, a trench waveguide 8 with a vertical DFB structure, an organic gain layer 9, a binder layer 11, and a light incident layer 10. Here, the bottom of the frame 13 may be supported by a substrate 12 (see Figure 8). Alternatively, the trench waveguide 8 may be formed so as to penetrate the frame 13 in the z direction. In this case, the opening forming the bottom of the trench waveguide 8 faces the substrate 12. The binder layer 11 functions as a transparent adhesive that does not absorb light, and amorphous fluoropolymers (e.g., CYTOP) can be used. The light incident layer 10 used for encapsulation is made of a hard and transparent material such as glass, a quartz sheet, or a sapphire sheet. Sapphire sheets are particularly suitable because they have high thermal conductivity. Of course, the materials constituting the substrate 12, the binder layer 11, and the light incident layer 10 are not particularly limited. By encapsulating (sealing), the OSL device 16 is protected from moisture and oxygen.

[0040] As described above, the frame 13 is made of, for example, SiO2, and one or more trench waveguides 8 are formed in the frame 13. The trench waveguide 8 extends in a direction intersecting (approximately perpendicular to) the light incident layer 10 and has two sidewalls 7 facing each other, and at least one sidewall 7 of the trench waveguide 8 is provided with a DFB grid 4 in which protrusions 5 and grooves 6 are repeatedly formed in the x direction (of course, as shown in Figures 5(B) and (C), the DFB grid 4 may be provided on each of the two sidewalls 7). An organic gain layer 9 (active layer) is deposited inside the trench waveguide 8. When ultraviolet light (UV) is incident on the light incident layer 10 from outside the OSL device 16, for example as excitation light, the organic gain layer 9 receives the energy of the ultraviolet light, generates excitons, forms a population inversion, and then undergoes stimulated emission. A high-power light-emitting diode (LED) or flash lamp may be used as the excitation light. In other words, the organic laser element 1 according to the second embodiment is a photo-excited (photo-pumped) organic solid-state laser that oscillates when excitation light is irradiated onto the organic gain layer 9. Since the substrate 12 supporting the frame 13 is usually glass, the excitation light may be incident from the substrate 12 side. That is, the substrate 12 can also function as the light incident layer 10.

[0041] As described above, the organic laser element 1 of the second embodiment comprises a light incident layer 10 into which light is incident, and a groove-shaped waveguide (trench waveguide 8) provided opposite to the light incident layer 10. The trench waveguide 8 is provided with a DFB grating 4 in which convex portions 5 and groove portions 6 are repeatedly formed. Each of the convex portions 5 and groove portions 6 extends in a direction that intersects (approximately orthogonal to) the light incident layer 10, and furthermore, the extension directions of the convex portions 5 and groove portions 6 intersect (approximately orthogonal to) the direction in which the waveguide extends toward the light emission surface. As a result, a highly efficient photo-excited organic laser element 1 (OSL device 16) is obtained in which light absorption loss and light leakage are reduced.

[0042] Furthermore, in the organic laser element 1 of the second embodiment, the waveguide (trench waveguide 8) extends in a direction intersecting (approximately perpendicular to) the light incident layer 10 and has two opposing sidewalls 7 (see Figure 5), and the DFB grating 4 may be provided on one sidewall 7 or on each of the two sidewalls 7. As a result, the DFB grating 4 functions as an optical resonator and generates laser light.

[0043] The following describes a modified version of the organic laser element 1 of the second embodiment. The modified version is an organic laser element 1 in which the light incident layer 10 and the binder layer 11 are removed from the configuration shown in Figure 9. In the modified version, the trench waveguide 8 is open (exposed) on the upper surface (first surface Sf1) of the frame 13, and the first surface Sf1 becomes the light incident surface. When excitation light is incident on the light incident surface, laser light is emitted from the light emission surface (second surface Sf2) which intersects (approximately orthogonal to) the light incident surface. Of course, the excitation light may also be incident from the side of the substrate 12. That is, the surface of the substrate 12 can also function as a light incident surface. The modified organic laser element 1 is housed, for example, in a chamber 39 (see Figure 10) filled with an inert gas.

[0044] Thus, a modified version of the second embodiment is an organic laser element 1 comprising a light incident surface (first surface Sf1) into which light is incident, a light output surface (second surface Sf2) intersecting the light incident surface, and a groove-shaped waveguide (trench waveguide 8) formed across the light incident surface and the light output surface, wherein the waveguide is provided with a DFB grid 4 in which convex portions 5 and groove portions 6 are repeatedly formed, and each of the convex portions 5 and groove portions 6 extends in a direction intersecting the light incident surface, and furthermore, the extension directions of the convex portions 5 and groove portions 6 intersect with the direction in which the waveguide extends toward the light output surface.

[0045] In the modified example, the waveguide (trench waveguide 8) extends in a direction intersecting (approximately perpendicular to) the light incident surface and has two opposing sidewalls 7 (see Figure 5), and the DFB grid 4 may be provided on one sidewall 7 or on each of the two sidewalls 7.

[0046] Figure 10 is an explanatory diagram showing the configuration of an inert gas-filled chamber (chamber 39) designed for end-face emission measurement, and Figure 11 is an explanatory diagram showing the configuration of an end-face emission measuring device 40 for measuring end-face emission from an OSL device 16. The OSL device 16 is placed in the chamber shown in Figure 10, and excitation light output from the pump laser shown in Figure 11 is incident on the light incident surface of the OSL device 16 through the first window 39w1. Of course, the OSL device 16 may be encapsulated, for example, when using a chamber 39 that is not filled with inert gas. In this case, the excitation light is incident on the trench waveguide 8 through the light incident layer 10 of the encapsulated OSL device 16. The excitation light may also be incident from the substrate 12 side.

[0047] As shown in Figure 11, the excitation light is focused linearly using an aperture 40c and multiple imaging optical systems 40d. However, it is difficult to form a laser beam that excites only the region of a single trench waveguide 8, and it is generally not possible to individually photoexcite trench waveguides 8 that have nanoscale dimensions. Therefore, in the evaluation of the OSL device 16, the characteristics are compared using a laser array with various dimensional parameters related to the trench waveguide 8. The laser light emitted from the end face of the trench waveguide 8 is output to the outside of the chamber 39 through the second window 39w2 and measured and evaluated by detectors 40b such as a multichannel spectrometer, a combination of a photomultiplier tube and an oscilloscope, a streak camera, a far-field characterization camera, and a Fourier back focal plane imaging detector.

[0048] (Third embodiment) Figure 12 is an explanatory diagram illustrating the overview of a conventional OSLD device with a horizontal DFB structure, and Figure 13 is a cross-sectional view of a conventional horizontal DFB structure including an OSLD. In Figure 13, the numerical values ​​attached to each component indicate the refractive index. The conventional OSLD device has an OLED structure, and an organic waveguide 30 including an organic gain layer 9 is arranged between a first electrode 2 made of ITO (Indium Tin Oxide) and a second electrode 3 made of metal. In the horizontal DFB structure, each convex portion 5 and each groove portion 6 of the DFB grid 4 extends in the y direction shown in the figure, along the plane (xy plane) of the first electrode 2 (or second electrode 3). Furthermore, each convex portion 5 and each groove portion 6 is repeatedly provided in the x direction. In Figure 12, the second electrode 3 is depicted as a flat plate, but in reality, as shown in Figure 13, the organic waveguide 30 undulates vertically in accordance with the pattern of the horizontal DFB structure, and the second electrode 3 formed on it by vacuum deposition also exhibits a wavy shape.

[0049] A periodic alternating pattern of high and low refractive indices, repeatedly arranged in the x-direction, functions as a feedback cavity (optical resonator), causing laser oscillation. The laser wavelength depends on the period of the DFB grating 4 (first-order DFB period P), the height of the convexity (PH), and the effective thickness df of the organic waveguide 30. Here, the first-order DFB period P is determined using Bragg's equation. According to Bragg's equation, first-order, second-order, and third-order or higher diffractions generate beam outputs in the x-direction, z-direction, and various angles in the zx plane, respectively.

[0050] The following describes the challenges of conventional OSLD devices. As shown in Figure 12, in conventional technology, the vibration direction of the TE mode wave (TE mode polarization) is parallel to the planes (xy planes) of the first electrode 2 and the second electrode 3, and is also parallel to the plane formed by the horizontal DFB structure. Since the ITO that constitutes the first electrode 2 has a high refractive index compared to most organic materials, some of the light propagating in the organic waveguide 30 leaks through the ITO slab, resulting in insufficient light confinement within the organic waveguide 30. In other words, the propagating light leaks into the high refractive index ITO, reducing the light confinement effect within the organic waveguide 30. The second electrode 3, which is made of a metal such as silver or aluminum, has high reflectivity, but evanescent waves penetrate the metal layer to some extent, causing absorption by metal atoms and ultimately hindering light amplification.

[0051] Furthermore, in a horizontal DFB structure, the refractive indices of the layers adjacent to the organic waveguide 30 differ significantly from each other. This results in an asymmetrical cross-section of the electromagnetic energy density distribution, causing significant penetration of evanescent waves into one of the adjacent layers. Therefore, it is important to either keep the hole-electron charge recombination zone Z in the organic waveguide 30 as far away from both electrodes as possible, or to prevent light leakage from the organic waveguide 30 by using a cladding layer. However, using a cladding layer in an organic device raises concerns not only about sputtering damage to the organic material, but also about insufficient charge carrier mobility in the cladding material (resulting in a significant increase in driving voltage).

[0052] Furthermore, in DFB structures, it is necessary to generate feedback by minimizing the height of the protrusions 5 (protrusion height PH) and reducing the perturbation of the induced wave. The smaller the protrusion height PH, the less scattering occurs in light propagation and the lower the laser threshold becomes. While lowering the protrusion height PH is optically advantageous, there are limitations to lowering the protrusion height PH in conventional horizontal DFB structures. This is because lowering the protrusion height PH reduces the insulating properties of the DFB lattice 4, which is composed of SiO2, and tunnel current may pass through the thin SiO2 layer. In particular, when the device is driven with a high current (voltage), leakage current or tunnel current may occur, and the heat generated may destroy the horizontal DFB structure.

[0053] On the other hand, in the trench waveguide 8 having a vertical DFB structure, since the DFB grid 4 is engraved on the side wall portion 7 of the waveguide, there is no restriction on lowering the protrusion height PH (see Figure 14(C)), and the laser oscillation threshold can be lowered by reducing the protrusion height PH. Thus, the organic laser element 1 of the third embodiment has improved stability and a longer operating life. Furthermore, the protrusion height PH can be minimized to zero. Clearly, this makes it possible to form a smooth and flat side wall portion 7 that produces current-injection amplified spontaneous emission (ASE) as described in the first embodiment, rather than stimulated emission (laser).

[0054] Furthermore, by forming the OLED structure with a greater thickness compared to conventional structures (e.g., 200nm-250nm), it is possible to prevent charge carriers from reaching the counter electrode. This improves the external quantum efficiency (EQE) and device stability.

[0055] Furthermore, it is difficult to incorporate an arbitrary OLED structure into a horizontal DFB structure. This is because changing the components of the OLED structure, such as the charge injection layer, charge transport layer, and charge blocking layer, simultaneously changes the charge transport capability and refractive index, affecting the optical confinement function of the organic waveguide 30. Therefore, in conventional OSLD devices employing a horizontal DFB structure, it is necessary to design the OSLD individually according to the characteristics of the materials constituting the OLED structure.

[0056] Furthermore, in order to overcome the high threshold, a large current injection may be performed, which could lead to the degradation of the element. In particular, when the thickness of the organic gain layer 9 is thin, the electric field between the two electrodes becomes relatively high, and the breakdown voltage of the element becomes low. The organic laser element 1 of the third embodiment was devised to solve these problems of the conventional technology, and its purpose is to provide an organic laser element 1 that is highly efficient by reducing optical absorption loss and optical leakage in the organic waveguide 30, as well as having a low threshold and a long operating life.

[0057] Figures 14(A) to (D) are explanatory diagrams showing the configuration of an organic laser element 1 (OSLD device 17 including a vertical DFB structure) according to the third embodiment of the present invention. As shown in Figure 14, the organic laser element 1 comprises a pair of electrodes (first electrode 2, second electrode 3) and a groove-shaped waveguide (trench waveguide 8) provided between the two electrodes. When the direction in which the trench waveguide 8 extends over the trench length TL is defined as the longitudinal direction, laser light is emitted from the end face of the trench waveguide 8 in the longitudinal direction. In the third embodiment as well, the trench waveguide 8 has a shape that satisfies the conditions effective trench width ETW < trench height TH < trench length TL. Specifically, the effective trench width ETW may be 150 nm to 250 nm, the trench length TL may be 1 mm to 3 mm, and the trench height TH may be 500 nm to 2000 nm. The number of trench waveguides 8 provided in the organic laser element 1 is arbitrary, and in this case, the organic laser element 1 is equipped with five trench waveguides 8. Furthermore, similar to the second embodiment, the trench waveguides 8 are provided with a DFB grid 4 having repeatedly formed protrusions 5 and grooves 6.

[0058] Here, Figure 14(B) is an enlarged view of the cross-section FC shown in Figure 14(A), and Figure 14(D) is an enlarged view of the cross-section S shown in Figure 14(A). Figure 14(C) is an enlarged view of the cross-section in the frame 13 that is perpendicular to the cross-sections FC and S. As shown in Figure 14(D), each trench waveguide 8 has two sidewalls 7 that extend in a direction intersecting (approximately perpendicular to) the first electrode 2 and the second electrode 3, and as shown in Figure 14(C), a DFB grid 4 is provided on at least one of the sidewalls 7. The sidewalls 7 that do not have a DFB grid 4 are smooth surfaces. Also, as shown in Figure 14(B), the convex portions 5 and groove portions 6 that constitute the DFB grid 4 provided in the trench waveguide 8 are each extended in a direction intersecting (perpendicular to) the first electrode 2 and the second electrode 3. Furthermore, the convex portions 5 and groove portions 6 are repeatedly formed in the longitudinal direction of the trench waveguide 8 (the direction in which the light emission surface is provided). With this configuration, the vibration direction of the TE mode wave is perpendicular to the first electrode 2 and the second electrode 3, that is, parallel to the extension direction of the convex portion 5 and groove portion 6 of the DFB grid 4. As a result, laser oscillation is performed by the vertical DFB structure, and optical absorption loss and optical leakage in the trench waveguide 8 are reduced.

[0059] In the third embodiment, the DFB grid 4 may be provided on one of the two opposing sidewall portions 7, or on each of the two sidewall portions 7. Furthermore, when the phase in which the convex portions 5 and groove portions 6 of the DFB grid 4 provided on one sidewall portion 7 are repeated is defined as the first phase, and the phase in which the convex portions 5 and groove portions 6 of the DFB grid 4 provided on the other sidewall portion 7 are repeated is defined as the second phase, the first phase and the second phase may be the same, the first phase and the second phase may be inverted, or the first phase and the second phase may be appropriately shifted between being the same and inverted. That is, the organic laser element 1 of the third embodiment can employ the vertical DFB structure described in Figures 5(A) to (C).

[0060] Figure 15 is a microscopic image of a trench waveguide 8 array with a vertical DFB structure formed on ITO. As shown in the figure, in the third embodiment, several thousand trench waveguides 8 with a vertical DFB structure are formed in an array by patterning a thick layer of SiO2. The thickness of the SiO2 (i.e., the thickness of the frame 13) can be, for example, 500 nm to 2000 nm.

[0061] Figure 16 is a cross-sectional view of the OSLD device 17 including a vertical DFB structure, and Figure 17 is an explanatory diagram illustrating the manufacturing process of the OSLD device 17. Hereinafter, the configuration and manufacturing process of the organic laser element 1 (OSLD device 17) of the third embodiment will be described in detail using Figures 14 in conjunction with Figures 14 and 16. Figure 16 is a detailed representation of the cross-section S shown in Figure 14(D). In Figure 16, the numerical values ​​attached to each component indicate the refractive index.

[0062] First, a fused silica glass (substrate 12) is prepared. An ITO layer (first electrode 2) is formed on the substrate 12. The thickness of the ITO layer is, for example, about 100 nm. Next, using a rectangular shadow mask, an SiO2 layer, which is the material that constitutes the frame 13 (see Figure 14), is formed by sputtering on the patterned ITO layer. In the third embodiment as well, the SiO2 layer is formed to be very thick (here, for example, 1 μm). Next, a resist layer is formed on the SiO2 layer using a spin coating method. Then, the EB (Electron Beam) resist layer, after exposure with electron beam lithography, is developed to create a nanopattern mask, and further reactive ion plasma etching and solvent cleaning are performed to create a trench waveguide 8 with a vertical DFB structure.

[0063] The plasma etching conditions at this time are optimized to remove SiO2 from the etched trenches and obtain a substantially clean ITO surface. This forms trench waveguides 8 (waveguide array 15) in the frame 13, and DFB grids 4 (primary vertical DFB) are formed on its side walls 7. It is preferable that the material constituting the frame 13 satisfies the conditions (I) to (IV) described in the second embodiment.

[0064] Next, each layer constituting the OLED structure, including the organic laser amplification material (organic gain layer 9), is deposited inside the trench waveguide 8 and the vertical DFB structure until the thickness is equal to or exceeds that of the SiO2 layer. Specifically, as shown in Figure 16, on top of the ITO layer (first electrode 2) formed on the glass substrate (substrate 12), the following layers are deposited in order: for example, a HATCN layer, a molybdenum oxide (MoO3) layer, the organic laser amplification material (organic gain layer 9), a cesium (Cs) doping layer, and an aluminum layer (second electrode 3). This completes the OLED structure. That is, the trench waveguide 8 constitutes an organic waveguide including the organic gain layer 9. As the gain material constituting the organic gain layer 9, the organic material described in the second embodiment can be used, and in addition, the inorganic material or organic-inorganic hybrid material described in the second embodiment can be used instead of the organic material. The thickness of the gain layer using these materials can be appropriately adjusted in the range of 500 nm to 3000 nm depending on the charge carrier conductivity of the gain material.

[0065] The frame 13 and substrate 12, which include the trench waveguide 8 (waveguide array 15) on which the OLED structure is formed, are cut along the CD line shown in the figure in a glove box filled with inert gas. In the third embodiment as well, the number of trench waveguides 8 formed in the above-described process is arbitrary and can be, for example, one, two, or more. In this way, an organic laser element 1 (OSLD device 17) that emits laser light from the cut surface (end face) is obtained. The obtained organic laser element 1 is fixed in a chamber filled with inert gas in order to measure its characteristics. Alternatively, it can be sealed and encapsulated.

[0066] In this OLED structure, very thin charge injection layers (functional layers) such as the HATCN layer, molybdenum oxide layer, and Cs doping layer are included, forming ohmic contacts at the interface between the electrode and the material constituting the organic gain layer 9, facilitating the injection of both holes and electrons. The injected holes and electrons recombine in a charge recombination zone Z (see Figure 16) sufficiently far from the first electrode 2 and the second electrode 3, and the exciton generation and deactivation (luminescence) process proceeds. Thus, in the organic laser element 1 of the third embodiment, an organic gain layer 9 made of an organic gain material is provided in the waveguide (trench waveguide 8), and at least one charge injection layer may be provided between the organic gain layer 9 and either electrode (first electrode 2 or second electrode 3) (see Figure 21(B)). This allows for high luminescence efficiency even when the thickness of the organic gain layer 9 is increased. Furthermore, a charge transport layer may be provided between the charge injection layer and the organic gain layer 9 (see Figure 21(A)). This allows for even higher luminescence efficiency.

[0067] Figure 18(A) is an explanatory diagram of the OLED structure used for evaluation, and (B) and (C) are characteristic diagrams of OLEDs with varying EML thicknesses from 200 nm to 1400 nm. As shown in Figure 18(A), the thickness of the ITO layer (first electrode 2) was fixed at 100 nm, the molybdenum oxide (MoO3) layer at 10 nm, the cesium (Cs) doping layer at 10 nm, and the aluminum layer (second electrode 3) at 1000 nm, while the thickness of the organic gain layer 9 was varied between 200 nm and 1400 nm to create multiple OLED samples.

[0068] Figure 18(B) shows the current-voltage-luminance (IVL) characteristics for each sample. As shown, the drive voltage and turn-on voltage are equivalent up to a thickness of 1 μm due to ohmic contact on both electrode surfaces. However, when the thickness of the light-emitting layer (organic gain layer 9) exceeds 1 μm, the distance between electrodes increases and the electric field decreases, causing a slight increase in the drive voltage and turn-on voltage. Figure 18(C) shows the current density-external quantum efficiency (EQE) characteristics for each sample. As shown, as the thickness of the light-emitting layer of a single-layer OLED increases, the carrier (charge) recombination efficiency improves, and therefore the external quantum efficiency improves. All OLEDs described using Figure 18 can be introduced into a trench waveguide 8 equipped with the vertical DFB structure described above.

[0069] As described above, the organic laser element 1 of the third embodiment comprises two electrodes (first electrode 2, second electrode 3) and a trench-shaped waveguide (trench waveguide 8) provided between the two electrodes. The trench waveguide 8 is provided with a DFB grid 4 in which protrusions 5 and grooves 6 are formed repeatedly (alternatingly) a predetermined number of times, and each of the protrusions 5 and grooves 6 extends in a direction intersecting (substantially orthogonal to) the electrodes. This results in a highly efficient organic laser element 1 with reduced light absorption loss and light leakage.

[0070] Furthermore, in single-layer or multi-layer OLED structures, a very thick (e.g., 600-1200 nm) organic gain layer 9 (organic laser active layer) limits the possibility of moving charge carriers reaching the counter electrode. This improves charge confinement and enables high external quantum efficiency (EQE). In addition, increasing the separation distance between the first electrode 2 and the second electrode 3 reduces the electric field in the organic gain layer 9, increasing the diode breakdown voltage.

[0071] Figure 19 is an explanatory diagram showing the configuration of an end-face emission measurement device 40 for measuring end-face emission from an OSLD device 17. The characteristics of the OLED described in Figure 18 can be measured, for example, by the end-face emission measurement device 40 shown in Figure 19. The end-face emission measurement device 40 includes a pulse generator 40a, which generates a drive signal with a preset voltage and ON duty cycle (pulse width), and supplies this drive signal to the first electrode 2 (anode) and the second electrode 3 (cathode) of the OSLD device 17. Based on the drive signal, light is generated in the organic gain layer 9 within the trench waveguide 8 that constitutes the waveguide array 15, and laser light is emitted from the end face of the trench waveguide 8, which acts as an optical resonator. The emitted laser light is measured by a detector 40b described using Figure 11. As mentioned above, in the OSL device 16 of the second embodiment, it is difficult to emit laser light from only a single trench waveguide 8. However, in the OSLD device 17 of the third embodiment, electrical excitation can be switched ON / OFF at the level of each individual trench waveguide 8. Specifically, by applying an active matrix circuit, for example, used in displays, the oscillation (emission) and stopping of laser light can be controlled at the level of each individual trench waveguide 8.

[0072] The desirable oscillation wavelength of the organic laser element 1 in the second and third embodiments is determined by the first-order DFB period P (see Figures 6 and 14(C)) calculated using the first-order Bragg equation, based on the emission profile of the optical gain material in the organic gain layer 9, the ASE peak wavelength, and the effective refractive index of the optical resonator including the DFB grating 4. In the organic laser element 1 of the third embodiment, i.e., the current-injection type organic semiconductor laser element, the threshold can be further reduced by optimizing the following. <Parameters related to the vertical DFB structure> ·Primary DFB period P • Pitch height of DFB grid 4 (height of protrusion PH) • Types of patterns for DFB grid 4 (see, for example, Figures 5(A) to (C)) <Parameters related to trench waveguide 8> • Effective trench width ETW • Trench length TL Trench height TH <Parameters related to the arrangement of trench waveguide 8> Trench spacing TS • Number of trench waveguides 8: N

[0073] Furthermore, the threshold of the organic laser element 1 can be further lowered by using the optimal pulse width during operation. Additionally, a longer pulse duration allows for maximum charge injection and maximum population inversion. Conversely, a shorter pulse duration reduces the accumulation of non-luminescent excited triplets and the generation of Joule heat.

[0074] Figure 20 is an explanatory diagram showing examples of organic gain materials used in the light source 25 of the first embodiment and the organic laser element 1 of the second and third embodiments. As shown in the figure, examples of green materials include C545T (Coumarin 545T:10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H-[1]benzopyrano[6,7,8-ij]quinoridine-11-one), examples of red materials include DCJTB (2-tert-butyl-4-(dicyanomethylene)-6-[2-(1,1,7,7-tetramethyljurolidine-9-yl)vinyl]-4H-pyran), and examples of blue materials include BSBCz (4,4′-bis[4-(9H-carbazole-9-yl)styryl]biphenyl). Of course, the light-emitting materials used are not limited to these. Furthermore, by doping BSBCz with C545T or DCJTB, green and red colors with efficient fluorescence resonance energy transfer (FRET) can be obtained. In the organic laser element 1 of the second and third embodiments, the primary DFB period P (see Figures 6 and 14(C)) is changed according to the required emission color.

[0075] Figure 21(A) is an explanatory diagram showing an example configuration of a multilayer OLED introduced into the OSLD device 17, and Figure 21(B) is an explanatory diagram showing an example configuration of a single-layer OLED introduced into the OSLD device 17. As shown in Figure 21(B), the organic gain layer 9 included in the OSLD device 17 may be a single-layer OLED structure comprising a hole injection layer (HIL), an emissive layer (EML) made of organic material, and an electron injection layer (EIL). Alternatively, as shown in Figure 21(A), it may be a multilayer OLED structure further comprising a hole transport layer (HTL) and an electron transport layer (ETL) as functional layers. In other words, in the first and second embodiments, any OLED structure such as a single-layer OLED, a double-layer OLED, or a multilayer OLED can be introduced into the trench waveguide 8 having a vertical DFB structure.

[0076] As described above, spontaneous emission (ASE) amplified by the light source 25 according to the present invention can be obtained, and the basic structure of the light source 25 (trench waveguide 8) can be applied to the amplification of light by stimulated emission (laser). Furthermore, the following effects can be obtained with the organic laser element 1 according to the present invention. (1) Practical photo-excited organic solid-state lasers (OSLs) or current-injection organic semiconductor laser diodes (OSLDs) can be obtained. (2) The laser wavelength can be adjusted by changing the primary DFB period P. In OSLD, furthermore, (3) This enables the realization of an organic laser element 1 that is compatible with all types of OLED structures. (4) Increasing the thickness of the OLED structure (organic gain layer 9) improves the stability of the device and extends its operating life. (5) The trench waveguide 8 made of SiO2 provides excellent light confinement, and the electromagnetic energy density distribution is symmetrical, allowing for a lower threshold current. (6) The threshold can be lowered by optimizing the pitch height (protrusion height PH) of the vertical DFB structure. [Industrial applicability]

[0077] The light source 25 and organic laser element 1 according to the present invention have reduced light absorption loss and light leakage, and are highly efficient, so they can be widely used in photonic circuits (optical integrated circuits), optical sensors, optical communications, spectroscopic devices, and the like. [Explanation of Symbols]

[0078] 1. Organic laser element 2 1st electrode 3 Second electrode 4 DFB lattice 5. Convex part 6 grooves 7 Side wall section 8 Trench Waveguides 9 Organic gain layer 10 Light entrance layer 11. Binder layer 13 Frame 15 Waveguide Array 16 OSL devices 17 OSLD devices 25 light source TL Trench Length TS trench spacing TH Trench Height ETW Effective Trench Width PH protrusion height P Primary DFB period

Claims

1. It comprises a groove-shaped waveguide formed to a predetermined length (trench length TL), a predetermined width (effective trench width ETW), and a predetermined height (trench height TH), The waveguide is, Effective trench width ETW < Trench height TH < Trench length TL Satisfying the relationship, When the longitudinal direction is defined as the direction in which the waveguide extends over the trench length TL, The waveguide has smooth side walls that are parallel and opposite to each other along the longitudinal direction, and the light source is characterized in that it emits naturally radiated amplified light from the end face of the waveguide in the longitudinal direction.

2. The effective trench width ETW is set to 150 nm to 250 nm. The trench length TL is 1 mm to 3 mm. The trench height TH is set to 500 nm to 2000 nm. The light source according to claim 1, characterized in that it is provided as follows.

3. The light source according to claim 1 or 2, characterized in that the refractive indices of the opposing side walls are the same.

4. The light source according to claim 3, characterized in that the waveguide is filled with a gain material having a refractive index higher than that of the side wall portion.

5. The light incident surface into which light enters, A light emission surface intersecting the light incidence surface, The system comprises a groove-shaped waveguide formed across the light incident surface and the light emission surface, The waveguide is provided with a DFB grid in which convex portions and groove portions are repeatedly formed. Each of the aforementioned protrusions and grooves is extended in a direction intersecting the light incident surface, Furthermore, the organic laser element is characterized in that the extension directions of the convex portion and the groove portion intersect with the direction in which the waveguide extends toward the light emission surface.

6. The waveguide is provided with two side walls that extend in a direction intersecting the light incident surface and are opposite to each other. The organic laser element according to claim 5, characterized in that the DFB grating is provided on one of the side walls.

7. The waveguide is provided with two side walls that extend in a direction intersecting the light incident surface and are opposite to each other. The organic laser element according to claim 5, characterized in that the DFB grating is provided on each of the two side wall portions.

8. Two electrodes, A groove-shaped waveguide is provided between the two electrodes, The waveguide is provided with a DFB grid in which convex portions and groove portions are repeatedly formed. An organic laser element characterized in that the convex portion and the groove portion are each extended in a direction intersecting the electrode.

9. The waveguide has two side walls that extend in a direction intersecting the electrode and are opposite to each other. The organic laser element according to claim 8, characterized in that the DFB grating is provided on one of the side walls.

10. The waveguide has two side walls that extend in a direction intersecting the electrode and are opposite to each other. The organic laser element according to claim 8, characterized in that the DFB grating is provided on each of the two side wall portions.

11. The waveguide is provided with a gain layer made of a gain material, The organic laser element according to claim 8, characterized in that the thickness of the gain layer between the two electrodes is 500 nm to 3000 nm.

12. The organic laser element according to claim 11, characterized in that at least one charge injection layer is provided between the gain layer and one of the electrodes.

13. The waveguide is formed to a predetermined length (trench length TL), a predetermined width (effective trench width ETW), and a predetermined height (trench height TH), The waveguide is, Effective trench width ETW < Trench height TH < Trench length TL Satisfying the relationship, When the longitudinal direction is defined as the direction in which the waveguide extends over the trench length TL, The organic laser element according to claim 5 or 8, characterized in that it emits laser light from the end face in the longitudinal direction of the waveguide.

14. The effective trench width ETW is set to 150 nm to 250 nm. The trench length TL is 1 mm to 3 mm. The trench height TH is set to 500 nm to 2000 nm. The organic laser element according to claim 13, characterized in that it is such that

15. The organic laser element according to any one of claims 6, 7, 9, or 10, characterized in that the refractive indices of the opposing side walls are the same.

16. The organic laser element according to claim 15, characterized in that the waveguide is provided with an organic gain layer made of an organic gain material having a refractive index higher than that of the side wall portion.

17. The phase in which the convex portion and the groove portion of the DFB grid provided on one of the side walls are repeated is defined as the first phase. The phase in which the convex portion and the groove portion of the DFB grid provided on the other side wall are repeated is called the second phase. When, The organic laser element according to claim 7 or 10, characterized in that the first phase and the second phase are the same.

18. The phase in which the convex portion and the groove portion of the DFB grid provided on one of the side walls are repeated is defined as the first phase. The phase in which the convex portion and the groove portion of the DFB grid provided on the other side wall are repeated is called the second phase. When, The organic laser element according to claim 7 or 10, characterized in that the first phase and the second phase are inverted relative to each other.

19. The phase in which the convex portion and the groove portion of the DFB grid provided on one of the side walls are repeated is defined as the first phase. The phase in which the convex portion and the groove portion of the DFB grid provided on the other side wall are repeated is called the second phase. When, The organic laser element according to claim 7 or 10, characterized in that the first phase and the second phase are shifted between being the same and being inverted.

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